Bonded filter block, its preparation and use



Patented Apr. 21, 1953 um'rso s'ra'rss PATENT orrlcs aolvnsn mrlm abocx.rra rssraas'rlon arm can Bonthwick W. Briggs, Bethesda, Md. No Drawing.Application July 0, 1048, serial No. 81,911

18 Claim!- (CL 196-147) 1 This invention relates to a filter material,and It is also an object this invention to provide more particularly toa porous block .having ada filter block which may be prepared at a lowcost. sorptive properties. with these and other objects in mind whi IDuring the operation 0! machinery. part cuwill become a parent in thefollowing detailed larly internal combustion engines, thelubridescription, this invention resides in the prepacant employed toovercome friction between bearration of a porous filter mass or an oxideor alu-, ing suriaces becomes contaminated with gums, minum bonded withcement. The bonded mass is acids and moisture, resulting primarily fromthe activated after the bonding operation to provide oxidation of thelubricant. It is desirable to rea porous material having strongadsorptive propmove these materials from the lubricant in order erties.

that it may maintain its lubrication properties In the preparation ofthe porous, adsorbent and to eliminate corrosion resulting from thefilter blocks oi this invention a hydrated oxide of presence of theimpurities. aluminum. preferably in a dry condition, is first Filtermaterials consisting oi loose beds or mixed with dry cement. While thealuminum products having strong adsorptive properties were oxide ispreferably physically dry at the time of first provided for purificationoi the oil. These mixin with the cement. it should be in a hylcose bedsof filter material were not satisfactory drated. unactivated conditionto obtain a finished ya because the fiuid being filtered tended tochannel product having maximum physical strength.

through the filter bed. The how of the fiuid Typical of the hydratedoxides which may be em- -causes movement of the loose adsorbent par-' 20ployed are bauxite and Grade C40 aluminum ticles during the filtrationwhich results in their hydrate distributed by the Aluminum Companyattrition and removal from the filter mass. The 0! America. Thesematerials contain approximovement of the particles also results inclassimately volatile material which is largely refication ot theadsorbent which in turn aggravates moved during the activation. thechannelling oi the fiuid passin through the The particle size or thehydrated oxide will defilter mess. I pend on the characteristics desiredin the fin- Many of the objections listed above have been ished filterblock. For example, a particle sise overcome by the use 01 adsorptiveminerals, such of 20-40 mesh on United states standard mea s asactivated alumina bonded to form porous rigid is t ry for th removal ofmoisture and blocks. Uniortunately. the bonded filters have so solidparticles from lubricating oil but does not not been as efiectiveadsorbents as the loose maimpar a "p lish" to the oil. I! a hydratedaluterial. Apparently. the bonding agent enters the minum oxide having aparticle size of 60-100 capillaries in the adsorbent and thereby dreases mesh is used, lubricating oil filtered therethrough theireiiectiveness. receives a high "polish."

A further objection to the porous filter blocks a The cement used in thebonding of the alumihitherto available has been the dimeulty in mm oxidei o din Port nd cement used for handling the bonding agent; d in tconstruction purposes and throughout this delecture or the blocks.Generally, these materials eeriviion the term "c ment" de ignatesmatehave geen highly corrosive and either strongly 9! that W- 31811Strength m n acidic or strongly alkaline. Moreover, the bond- 40 M11 I8moor. may also be used and a r f rr d jng agents a mum ilicate andbecause Of the short m required 101' initial phosphate, are very stickyand m k c m set of the bond. A typical analysis of an Incor mama; mm and0mm m m cement which has been used in the preparation It is an object ofthis invention to provide a bloc hum": strong. porous filter block inwhich the adsorbent a 1932 is bonded firmly in place. 1,oe 554 Anotherobject of this invention is to provide Peso: 2.74 a porous stronglyadsorbent filter block. CaO 83.80 A further object c! this invention isto provide M8 7 8.26 a filter block which may be mechanically com- 502.8! pounded in automatic machinery. still another obieo o th inve on isto p The cement is mixed with the adsorbent mavide a strongly adsorbentfilter medium which terial in anpunts ranging from about 15 to may bereactivated without loss 0! its adsorpoi the. adsorbent. The minimumamount 0! cetive properties. V 6 mentwillbe determined by the minimumphysical strength required by the porous block. Blocks prepared from amixture containing cement are too fragile to be handledcommercially, andabout cement is the lowest concentration which may be used for mostpurposes.

'If the concentration of the cement in the block is increased, nodefinite adverse eifects upon the adsorption have been noted up toconcentrations of as high as 45%. However, an increase in the cementdecreases the porosity of the adsorbent block and a tendency for surfacefiltration arises. The total dirt capacity will then be decreased by thedeposition of dirt on the surface and blocking of flow through adsorbentblocks containing high cement concentrations. Generally it is preferableto use mixes in which the cement amounts to about of the hydratedaluminum oxide.

When activated alumina is bonded with cement, it is necessary toincrease the concentration of the cement in order to provide anadsorbent block with sufficient physical strength. An adsorbent blockprepared from a mix in which the weight of cement is about 30% of theweight of the activated alumina has suificient strength to be usedcommercially. but must be handled carefully. No loss in adsorptiveproperties is noted when the alumina is activated prior to bonding. Itwill, however, be necessary to reactivate the adsorbent after bonding.

Sometimes dii'ilculty is encountered in preparing adsorbent blockshaving satisfactory strength from natural occurring bauxites. Thebauxite may be washed with a 5%solution of sodium silicate and thewashed material dried at 230240 F. prior to bonding with cement toobtain a stronger product.

Both the hydrated Oxide of aluminum and the cement are dry powders whichmay be easily handled in automatic weighing machinery withoutdifliculty. These materials fiow freely, are not sticky even after theaddition of water, and may be completely removed from the apparatuswithout difficulty. This is in contrast with materials such as the acidaluminum phosphates or sodium silicate which are highly viscous andtacky and tend to build up on the equipment if they are used. Moreover,no serious safety or corrosion problems are encountered in the hantilingof aluminum oxide-cement mixtures.

Water, amounting to about 20% of weight of the aluminum oxide. isthoroughly mixed with the aluminum oxide and cement mixture. The watermay be added to either of the solid materials before the solid materialsare mixed, but it is generally desirable to handle the materials in adry state during as much of the operations as possible. A reduction inthe water content to about 10% of the weight of the aluminum oxide,while the amount of cement remains constant. results in a decrease inthe strength and adsorptivity of the block. On the other hand, anincrease in the amount of water to causes only a slight reduction.

.The wet mixture of the aluminum oxide and cement are then formed in anydesired shape. The forming operation will usually consist of packing themixture in molds in which the mixture is allowed to stand until initialset of the cement has occurred. The mixture may be packed in the mold bymeans of a press, vibrating table or any other suitable apparatus. Ifthe mixture is packed in the mold by means of a vibrating table andhigh-early-strength cement has been employed in the preparation of t themix, a setting period of approximately six hours is sumcient to allowthe blocks to be handled without breakage or smearing of their surfaceon handling. In most instances the blocks are aged for three days afterbeing removed from the mold before activation.

The bonded filter block of hydrated aluminum oxide and cement isactivated by heating to temperatures ranging from about 600 F. to about900 F. The blocks are suiliciently stable and strong to be heateddirectly from room temperature to 450 F. The blocks may be heated to thehigher temperatures required for activation at a rate of 1'. per hourwithout danger of cracking. No ceramic heating schedule is necessary inthe activation procedure. but the blocks should be maintained at theactivation temperature for a period sumcient to heat the entire mass ofthe block.

The particular temperature to which the block is heated for activationwill depend upon the purposes for which it is to be used. If the filterblock is primarily to adsorb moisture it may be heated to thetemperature of approximately 600 F. for about one hour. This temperatureis suificient to eliminate the volatile material from bauxite andaluminum hydrate to form a porous structure having excellent adsorptivecharacteristics. On the other hand, if the filter block is to be used inthe clarification of lubricating oils it is preferably heated totemperatures in the neighborhood of 900 F. A block heated to the highertemperature is very effective in removing asphaltenes from the oil.

The porous filter block prepared according to this invention isextremely effective as an adsorbent as well as a mechanical filter andhas a strong stripping action as compared with other adsorbents. Forexample. in tests on a refrigerant containing fifteen to twenty partsper million water treated with loose, activated silica gel. the watercontent was reduced to approximately five parts per million. The watercontent of this same refrigerant containing fifteen to twenty parts permillion and treated with looseactivated alumina was reduced toapproximately one part per million. If the alumina is bonded with cementin the manner described herein, the stripping capacity of the alumina isunimpaired and the bonded filter medium also reduced the water contentof the refrigerant to approximately one part per million. On the otherhand, alumina bonded with sodium silicate or acid aluminum phosphatesand then activated, reduced the water content of the refrigerant toapproximately two and one and one-half parts per million, respectively.

The filter medium prepared according to this invention possessesimportant advantages over prior bonded adsorbents in respect to itstotal capacity as well as its effectiveness in stripping. Actually, thetotal capacity of the alumina bonded with cement is higher than thecapacity of alumina in the loose form. Tests were run in which filterblocks bonded with acid aluminum phosphate, sodium silicate, and severalconcentrations of cement were exposed to an atmosphere of 98% relativehumidity at approximately 20 C. The amount of water adsorbed by theblocks was determined by their increase in weight and is presented inthe following table as per cent of the weight of the block. For purposesof the test, all of the test specimens were heated to 450 8landcooledtoroomtemperatureimmodiately before beinsexposed to the humidatmosphere:

6 lt willbesasnthatths'total capasityclths Ill adsorbent material bondedwith cement IohtmeAdsorbsd-Jsresutoi wsightoiadsca'bsnt Alisa-bentlernpsr Boursoilrpsanre 1% a 7! I I flmssaluminumhydrate U0 .1 :8 7.!0.4 10.1 14.!

Aluminum hydrate bonded -withaluminumpbosgh :t e 000 8.8 u 0.1 10.7 10.010.8 Aluminum hydrate witbaodiumsiiisate I10 1.8 5.0 LI 5.! ll 0.!

um hydrate bonded withimosmsnt 000 2.1 as 0.2 10.0 12.0 ms

um hydrate bonded withm t 000 4.5 It! 0.0 11.8 14.0 10.6

um hydrate bonded thafissmsnt 000 3.1 4.3 0.0 8.5 10.5 18.0Loossaluminumhydmts 050 1.8 0.5 8.0 0.1 0.! 11-! um hydrate bondedwithaluminump 650 3.8 5.5 1.5 0.0 10.2 10.0

um hydrate nded withaodiumsilicate 650 1.5 2.0 8.5 5.5 0.0 0.0 Al umhydrate bonded withl5%oement 050 3.2 5.7 5.. 11.4 18.5 17.5 Al umhydrate bonded withfifi csmeni 050 8.1 6.5 5.0 11.4 12.0 10.! Aluminumhydrate bonded withzs%cemeni 060 2.2 5.] 8.7 10.9 11.0 18.8

The test specimen oi loose aluminum hydrate was prepared by activatingthe loose material at the temperatures indicated in the table and thenplacing it in a perforated metal cylinder 30 three inches long and twoinches in diameter.

The aluminum phosphate bonded aluminum hydrate was prepared by mixingaluminum hydrate with 22%% 0! its weight 0! aluminum phosphate for aperiod of twenty minutes. The

aluminum hydrate and aluminum phosphate mixture wasmolded to form a testspecimen three inches long and two inches in diameter. The molded testspecimens were fired at 850 1'.

and at 900 1''. for two hours for the two tests. 40

The specimens were fired within eight hours after the molding operation.

The test specimens in which aluminum hydratc was bonded with sodiumsilicate were premolded to form a test specimen three inches lon and twoinches in diameter. The test specimens were fired at 650 F. and at 900F. for two hours within eight hours after their fabrication.

One of the cement bonded test specimens was prepared by mixing Grade0-40 aluminum hydrate with 15% of its weight oi lncor high-earlystrengthPortland cement for two minutes. Wa-

ter amounting to of its weight of aluminum hydrate was added to the drymix and the mixing continued ior five minutes. Test specimens threeinches long and two inches in diameter were formed. These test specimenswere aged !or seventy-two hours and then fired at 050 1''.

and at 900 I". (or two hours for the two tests. The test specimenscontaining cement and 20% cement were prepared in exactly the samemanner except for the proportion oi the cement.

The aluminum hydrate had a screen analysis on 95 United States standardsieves as follows:

Per cent Thru 20 on 56.17 Thru 35 on 27.71 'Zl'hru 45 on 7.09 Thru 50 on5.24 Thru 00 on pan 2.80

higherthanthatoitheloosematerialinallinstances. Whereas the bonding ofloose aluminum hydrate with sodium silicate or acid alumina ts resultsin the decrease oi the capacity of the adsorbent, the bonding withcement actually increases the total capacity of the porous filter mass.Apparently. the cement has adsorptive properties which are added to theadsorptive properties of the activated aluminum in this novel adsorbentmaterial.

when the specimens und in the tests set forth in the table above werereactivated by heating to activation temperatures. cement-bonded blocksregained their capacity for adsorbin moisture. One sample has beenreactivated tourteen times and continues to follow the initialabsorption curve. Apparently the increased abaorption is not the resultof absorption of water of erystallimtionby the cement during its initialset. The filter medium herein described may. thereiore, be periodicallyremoved irom service. reactivated. and returned to service withoutlosing its eiiectiveness.

The novel filter medium oi this invention is superior to the materialshitherto available in several important aspects. The strippin ability,

. as well as the total adsorptive capacity of the new material, issuperior to the bonded filter materials oi the prior art. In addition,important reductions in the cost 0! manuiacturing porous filter blockshaving adsorptive properties are made possible by the ease withwhich thematerials may be handled as well as the low cost of the raw materials.

While this invention has been described in detail with reference tospecific examples, it is to be understood that the invention is notlimited to those details but falls within the scope of the appendedclaims..

I claim:

l. A filter medium comprising a thermally activated bonded composition.said composition comprising about -85% hydrated oxide of aluminum 0bonded with about 15-35% Portland cement.

2. A filter medium comprising a thermally activated bonded composition,said composition comprising about 05-85% bauxite bonded with about15-35% Portland cement.

100.00 is 8. A filter medimn comprising a thermally activa'ted bondedcomposition, said composition comprising about 65-85% aluminum hydratebonded with about 15-35% Portland cement.

4. A method or making a filter block comprising mixing a hydrated oxidealuminum with Portland cement and water in proportions of about to 45parts of Portland cement to 100 parts of hydrated oxide of aluminum,forming the mixture in the desired shape 01' the block, and heating theformed block to temperatures sufficient for activation of the filterblock.

5. A method of making a filter block comprising mixing a hydrated oxideof aluminum with Portland cement in proportions of about 15 to 45 partsof Portland cement to 100 parts 0! hydrated oxide of aluminum, addingwater to the dry mixture forming the wet mix in a block of the desiredshape, storing the block to set the cement partially, and heating theset block to temperatures sufllcient for activation or the hydratedoxide of aluminum.

6. A method of making a filter block comprising mixing hydrated aluminumoxide with about 15- 45% of its weight of Portland cement. adding waterin the amount of about of the weight or the aluminum oxide, forming themixture in a block of the desired shape, and heating the block to atemperature of about 600-900 F. to activate the block.

7. A method of making a filter block comprising mixing a hydrated oxideof aluminum with about 15-45% of its weight oi Portland cement and about20% of its weight of water, forming a block oi the desired shape of thewet mixture, storing the block whereby the cement is partially set, andactivating the block by heating to a temperature or about 600-900 F. fora period or about one hour.

8. As a new composition of matter, a hydrated aluminum oxide bonded withPortland cement. said aluminum oxide and Portland cement being inproportions of about 15 to 45 parts of Portland cement to 100 parts ofaluminum oxide, said bonded aluminum oxide being heated to a temperatureof about GOO-900 F. after bonding.

9. An adsorptive monolithic filter medium comprising thermally activatedhydrated oxide of aluminum bonded with Portland cement, said cementbeing present in amounts ranging from about 15 to per cent of thecomposition.

10. An adsorbent monolithic filter medium comprising thermally activatedaluminum hy drate bonded with Portland cement, said cement being presentin amounts ranging from about 15 to 35 per cent of the composition.

11. A method of clarifying lubricating oils to remove moisture andimpurities therefrom, comprising passing the lubricating oil through amonolithic porous block of finely divided particles at a hydratedaluminum oxide bonded with Portland cement, said aluminum oxide andPortland cement being in proportions of about 100 parts of aluminumoxide to about 15 to parts of Portland cement, said block beingactivated by heating is a temperature or about 600 to 900 F.

12. A method or making a filter block comprising mixing a hydrated oxideof aluminum with Portland cement and water in proportions of about 15 to45 parts of water and cement to 100 parts of hydrated oxide of aluminum,forming the mixture in the desired shape of the block, and activatingthe thus formed block by heating to a temperature of about 600 to 900 F.

13. A method of making a filter block comprising mixing a hydrated oxideof aluminum with Portland cement in proportions of about 15 to 45 partsof Portland cement to parts of hydrated oxide or aluminum, adding waterto the dry mixture, forming the wet mix in a block oi the desired shape,stirring the block to set the cement partially, and activating the setblock by heating to a temperature of about 600 to 900 F.

BOUTHWICK W. BRIGGS.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 1,856,141 Stark May 3, 1932 2,007,052 Howe July 2, 19352,067,920 Heuser Jan. 19, 1937 2,249,681 Briggs et a1 July 15, 19412,292,632 Greger Aug. 11, 1942 Q m i

1.A FILTER MEDIUM COMPRISING A THERMALLY ACTIVATED BONDED COMPOSITION,SAID COMPOSITION COMPRISING ABOUT 65-85% HYDRATED OXIDE OF ALUMINUMBONDED WITH ABOUT 15-35% PORTLAND CEMENT.
 11. A METHOD OF CLARIFYINGLUBRICATING OILS TO REMOVE MOISTURE AND IMPURITIES THEREFROM, COMPRISINGPASSING THE LUBRICATING OIL THROUGH A MONOLITHIC POROUS BLOCK OF FINELYDIVIDED PARTICLES OF A HYDRATED ALUMINUM OXIDE BONDED WITH PORTLANDCEMENT, SAID ALUMINUM OXIDE AND PORTLAND CEMENT BEING IN PROPORTIONS OFABOUT 100 PARTS OF ALUMINUM OXIDE TO ABOUT 15 TO 45 PARTS OF PORTLANDCEMENT, SAID BLOCK BEING ACTIVATED BY HEATING TO A TEMPERATURE OF ABOUT600 TO 900* F.